One type of known polymer electrolyte membrane fuel cell (PEMFC), shown schematically in FIG. 1 of the accompanying diagrammatic drawings, may comprise a thin sheet 2 of a hydrogen-ion conducting Polymer Electrolyte Membrane (PEM) sandwiched on both sides by a layer 4 of platinum catalyst and an electrode 6. The layers 2, 4, 6 make up a Membrane Electrode Assembly (MEA) of less than 1 mm thickness.
In a PEMFC, hydrogen is introduced at the anode (fuel electrode) which results in the following electrochemical reaction:Pt-Anode (Fuel Electrode) 2H2→4H++4e−
The hydrogen ions migrate through the conducting PEM to the cathode. Simultaneously, an oxidant is introduced at the cathode (oxidant electrode) where the following electrochemical reaction takes place:Pt-Cathode (Oxidant Electrode) O2+4H++4e−→2H2O
Thus, electrons and protons are consumed to produce water and heat. Connecting the two electrodes through an external circuit causes an electrical current to flow in the circuit and withdraw electrical power from the cell.
The PEM 2 could comprise a single layer of ion-conducting material. However, in many cases, a single layer of material does not have satisfactory mechanical properties.
Many proposals have been made for improving the mechanical and other properties of ion-conducting materials for as PEMs. For example, U.S. Pat. No. 5,834,566 (Hoechst) solves the problem by providing homogenous polymer alloys based on sulphonated polyether ketones, whereby the absorption capacity for water and mechanical properties can be adjusted in a controlled manner by varying the components in the alloy and their respective ratios.